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Soybeans can be broadly classified as "vegetable" (garden) or field
(oil) types. Vegetable types cook more easily, have a mild nutty
flavor, better texture, are larger in size, higher in protein, and
lower in oil than field types. Tofu and soymilk producers prefer the
higher protein cultivars bred from vegetable soybeans originally
brought to the United States in the late 1930s. The "garden" cultivars
are generally not suitable for mechanical combine harvesting because
they have a tendency for the pods to shatter on reaching maturity.
Among the legumes, the soybean, also classed as an oilseed, is
pre-eminent for its high (38–45%) protein content as well as its high
(20%) oil content. Soybeans are the leading agricultural export in the
United States. The bulk of the soybean crop is grown for oil
production, with the high-protein defatted and "toasted" soy meal used
as livestock feed. A smaller percentage of soybeans are used directly
for human consumption.
Immature soybeans may be boiled whole
in their green pod and served with salt, under the Japanese name
edamame (edamame?). Soybeans prepared this way are a popular local
snack in Hawaii, and are becoming increasingly popular in the
continental United States. Because of the proclaimed health benefits
of soy, edamame has been featured as an ideal snack alternative in
fitness and healthy living magazines such as Real Simple. Edamame is
sold in the frozen vegetable section at some larger grocery stores,
and as ready-to-eat snackfood in many Asian delis.
In China, Japan, and Korea the bean and products made from the bean
are a popular part of the diet. The Chinese invented tofu, and also
made use of several varieties of soybean paste as seasonings. Japanese
foods made from soya include: miso , natto, and edamame. In Korean
cuisine, soybean sprouts, called kongnamul (hangul) are also used in a
variety of dishes such as doenjang, cheonggukjang and ganjang.
The beans can be processed in a variety of ways. Common forms of soy
(or soya) include soy meal, soy flour, soy milk, tofu, textured
vegetable protein (TVP, which is made into a wide variety of
vegetarian foods, some of them intended to imitate meat), tempeh, soy
lecithin and soybean oil. Soybeans are also the primary ingredient
involved in the production of soy sauce (or shoyu).
Soybeans grow throughout Asia and North and South America. Archer
Daniels Midland (ADM) is among the largest processors of soybeans and
soy products. ADM along with Dow Chemical Company, DuPont and Monsanto
support the industry trade associations United Soybean Board (USB) and
Soyfoods Association of North America (SANA). These trade associations
have increased the consumption of soy products dramatically in recent
years.
Chemical composition of the seed
The oil and protein content together account for about 60% of dry
soybeans by weight; protein at 40% and oil at 20%. The remainder
consists of 35% carbohydrate and about 5% ash. Soybean cultivars
comprise approximately 8% seed coat or hull, 90% cotyledons and 2%
hypocotyl axis or germ.
The majority of soy protein is a relatively heat-stable storage
protein. This heat stability enables soy food products requiring high
temperature cooking, such as tofu, soymilk and textured vegetable
protein (soy flour) to be made.
The principal soluble carbohydrates, saccharides, of mature soybeans
are the disaccharide sucrose (range 2.5–8.2%), the trisaccharide
raffinose (0.1–1.0%) composed of one sucrose molecule connected to one
molecule of galactose, and the tetrasaccharide stachyose (1.4 to 4.1%)
composed of one sucrpose connected to two molecules of galactose.
While the oligosaccharides raffinose and stachyose protect the
viability of the soybean seed from desiccation (see above section on
physical characteristics) they are not digestible sugars and therefore
contribute to flatulence and abdominal discomfort in humans and other
monogastric animals; compare to the disaccharide trehalose. Undigested
oligosaccharides are broken down in the intestine by native microbes
producing gases such as carbon dioxide, hydrogen, nitrogen, methane,
etc.
Since soluble soy carbohydrates are found mainly in the whey and are
broken down during fermentation, soy concentrate, soy protein
isolates, tofu, soy sauce, and sprouted soybeans are without flatus
activity. On the other hand, there may be some beneficial effects to
ingesting oligosaccharides such as raffinose and stachyose, namely,
encouraging indigenous bifidobacteria in the colon against
putrefactive bacteria.
The insoluble carbohydrates in soybeans consist of the complex
polysaccharides cellulose, hemicellulose, and pectin. The majority of
soybean carbohydrates can be classed as belonging to dietary fiber.
Soybean meal
Soybean meal, the material remaining after solvent extraction of
soybean flakes, with a 50% soy protein content, toasted (a misnomer
because the heat treatment is with moist steam) and ground in a hammer
mill, provided the energy for the American revolution, beginning in
the 1930s, of growing farm animals such as poultry and swine on an
industrial scale; and more recently the aquaculture of catfish.
Flour
Soy flour refers to defatted soybeans where special care was taken
during desolventizing (not toasted) in order to minimize denaturation
of the protein to retain a high Nitrogen Solubility Index (NSI), for
uses such as extruder texturizing (TVP). It is the starting material
for production of soy concentrate and soy protein isolate.
Defatted soy flour is obtained from solvent extracted flakes, and
contains less than 1% oil. Full-fat soy flour is made from unextracted,
dehulled beans, and contains about 18% to 20% oil. Due to its high oil
content a specialized Alpine Fine Impact Mill must be used for
grinding rather than the more common hammer mill.
Low-fat soy flour is made by adding back some oil to defatted soy
flour. The lipid content varies according to specifications, usually
between 4.5% and 9%.
High-fat soy flour can also be produced by adding back soybean oil to
defatted flour at the level of 15%. Lecithinated soy flour is made by
adding soybean lecithin to defatted, low-fat or high-fat soy flours to
increase their dispersibility and impart emulsifying properties. The
lecithin content varies up to 15%.
Substitute for existing products
Processed soybeans are the primary ingredient in many imitation foods,
including dairy products (e.g., margarine, soy ice cream, soy milk,
soy yogurt, soy cheese and soy cream cheese), as well as Crisco,
soybean oil, tofu, veggie burgers, soy crisps, among others. These
products are derived from extensive processing to produce a texture
and appearance similar to conventional foods (e.g., butter, ice cream,
milk, yogurt, cheese, lard, olive oil, ground beef, potato chips,
etc.) and are readily available in most supermarkets. Soy milk does
not contain significant amounts of calcium, since the high calcium
content of soybeans is bound to the insoluble constituents and remains
in the pulp. Many manufacturers of soy milk now sell calcium-enriched
products as well.
Other products
Soybeans are also used in industrial products including oils, soap,
cosmetics, resins, plastics, inks, crayons, solvents, clothing, and
biodiesel. Soybeans are also used as fermenting stock to make a brand
of vodka.
Henry Ford promoted the soybean, helping to develop uses for it both
in food and in industrial products, even demonstrating auto body
panels made of soy-based plastics. Ford's interest led to two bushels
of soybeans being used in each Ford car as well as products like the
first commercial soy milk, ice cream and all-vegetable non-dairy
whipped topping. The Ford development of so-called soy-based plastics
was based on the addition of soybean flour and wood flour to
phenolformaldehyde plastics.
In 1931, Ford hired chemists Robert Boyer and Frank Calvert to produce
artificial silk. They succeeded in making a textile fiber of spun soy
protein fibers, hardened or tanned in a formaldehyde bath which was
given the name Azlon by the Federal Trade Commission. Pilot production
of Azlon reached 5000 pounds per day in 1940, but never reached the
commercial market.
Today, very high quality textile fibers are made commercially from "okara"
(soy pulp), a by-product of tofu production.
Protein
Soybeans are generally considered to be a source of complete protein,
without any need for Protein combining.[23] although this is contested
by some sources. A complete protein is one that contains significant
amounts of all the essential amino acids that must be provided to the
human body because of the body's inability to synthesize them. For
this reason, soy is a good source of protein, amongst many others, for
many vegetarians and vegans or for people who cannot afford meat.
The gold standard for measuring protein quality, since 1990, is the
Protein Digestibility Corrected Amino Acid Score (PDCAAS) and by this
criterion soy protein is the nutritional equivalent of meat and eggs
for human growth and health. Soybean protein isolate has a Biological
Value of 74, whole soybeans 96, soybean milk 91, and eggs 97.[26]
Soy protein is similar to that of other legume seeds, but has the
highest yield per square meter of growing area, and is the least
expensive source of dietary protein.
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